Listers ... I started this thread off-line with Charlie Brown, but now that
it's getting
interesting, I thought I would copy it to the list. Originally, I asked him
about
autocrossing and what he has done to his very nice Spitfire (one of them) to
prep it for
autocrossing. He responded ...
>
> Martin,
>
> When I built the engine in the Weenie, I installed TR6 pistons as per
> the recommendations in the Comp Prep manual. The stock 6 pistons are a
> .040 over bore for a Spit engine. They are shorter, ergo lighter, to
> boot! Being shorter, you'll need to mill the block by about .165" to get
> back to zero deck height. Then you CC and polish the combustion chamber
> to balance the combustion processes. I CCed the chambers to 43ccs, which
> gives me a C/R of about 10:1. My current build, for my driver, will use
> the AE brand .040 over, flat top pistons. Apparently, the PO of this
> engine did some head work because when I CCed the head, I found myself
> with about 44ccs per chamber. So I'm going to be real close to the same
> 10:1 C/R.
> >Charlie:
If I actually do any engine internals, I would like to keep them simple; i.e.,
I think I
would opt for the 1976 flat-top piston swap out, rather than have to take the
whole
block out to be milled (!) Regardless, I haven't made any decisions yet, but I
would
like to do something worthwhile to increase the car's minimal torque.
> >Refresh my memory, what have you got for intake and exhaust? Are you
> running HS4s. Are you using some sort or header and free flow exhaust?
> As I've found out, you can have all the power in the world, but if you
> can't get that power to the asphalt, your cause is lost. Five inch
> wheels will really restrict your tire choice, unless you're planning to
> run a stock class. If you've made other performance modifications, stock
> classification is out (depending on who's series your running in). I got
> a set of TR7 wheels for my driver, which are 5-1/2". My plan is to
> transfer the 185 profile tires off the Weenie after a couple of years of
> autocrossing, after they've lost their "sticky", but still have a lot of
> tread. This year I'll be transferring the current Yoko A509s and
> replacing them with Yoko AVS Intermediates.
Here's what I have. I said 5-inch wheels -- I thought that's what they are --
but I
guess they are 5 1/2 inches wide. In any case, they are the TR7 stock steel
wheels,
with Yokohama 509's mounted. Very heavy. Total wheel weight is ... would you
believe
.. 30 pounds! Yikes! (One 14 inch Panasport, without tire, is 7 pounds. I
weighed one
at Motorhead this weekend.) As per the intake, I have twin HS6's (1.5 inch
SUs)
mounted, deep K&N's, with a Monza header, but only a stock exhaust train. I
know, I know
... what's the point of the header with the stock exhaust? I don't know ...
but for a
tight autocross course, I would imagine that the stretches requiring high revs
-- where
free flow helps the most -- are relatively rare?
>
> Anything you do to improve spark will help. The better the spark the
> better the combustion. But, like I said, all the power in the world is
> usless unless you can transfer that power to the ground. In
> autocrossing, grip is everything. I would forgo a little more power for
> a little more grip. A rear anti-sway bar is a good investment.
>
> If you want to try autocrossing, give it a shot. I, personally, have a
> ball. Whenever a "newbie" asks for advice, the first thing I tell them
> is to concentrate on the course first. When you're sitting behind the
> wheel, finding the correct path through the cones at speed can be very
> daunting. Every month the course changes. Learning to memorize a course
> quickly becomes mandatory. If you go off course, it's a DNF.
> Walk-throughs, before each event, are important. Concentrate on learning
> the course. When you're done, stand there, look out over the cones, and
> run the course in you mind.
>
> Learn to finish on course, speed will come later.
That's pretty much what I figured.
On the other hand, maybe I'll just go out there in the GT6 ...
--
Martin
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